Abstract : The investigation of microwave delay processes in ferrimagnetic materials is described that includes magnetostatic and magnetoelastic waves. Emphasis was placed on the development of two-part devices based on the transmission mode of magnetoelastic wave propagation. In order to compensate for the conversion losses and medium attenuation a parallel study of the parametric amplification of elastic and magnetoelastic waves was undertaken. As a result of these studies, it has been demonstrated that variable delay lines with net gain are feasible at room temperature in the microwave frequency range. (Author)